
 function ajax (url, data={}, type='GET') {

    return new Promise(function (resolve, reject) {
        // 执行异步ajax请求
        type = type.toUpperCase()
      console.log(type)
        let promise
        if (type === 'GET') {
            // 准备url query参数数据
            let dataStr = '' //数据拼接字符串
            Object.keys(data).forEach(key => {
                dataStr += key + '=' + data[key] + '&'
            })
            if (dataStr !== '') {
                dataStr = dataStr.substring(0, dataStr.lastIndexOf('&'))
                url = url + '?' + dataStr
            }
            // 发送get请求
            promise = axios.get(url)
        } else if(type === 'POST'){
            // 发送post请求
            promise = axios.post(url, data)
        }else if(type === 'PUT'){
            promise = axios.put(url, data)
        }else if(type === 'DELETE'){
            promise = axios.delete(url)
        }
        if (promise != null) {
            promise.then(function (response) {
              // 成功了调用resolve()
              resolve(response.data)
            }).catch(function (error) {
              //失败了调用reject()
              reject(error)
            })
        }
    })
}
